Optical transmission systems constitute the basic carrier for most telecommunication systems. Many optical transmission technologies are based on the principle of wavelength division multiplexing (WDM) or Dense WDM (DWDM), where the transmission channels are carried by optical signals over different wavelengths or different bands of wavelengths. In some WDM or DWDM systems, it is desirable to use a colorless WDM or DWDM transmitter that uses a plurality of colorless laser transmitters to provide a plurality of different wavelength channels. The colorless WDM or DWDM transmitter comprises a plurality of filters that have different band-pass spectra configured to select different wavelength bands from the colorless laser transmitters to provide the different wavelength channels. Similar or identical laser transmitters can be used to provide the different wavelengths. Different types of laser transmitters can also be used without changing the wavelength channels.